We are on leading edge of the space time continuum
How do you view the timeline of the history of life on Earth?
- Starts at early life?
- where is that?
- Is your view biased towards human existence?
- What processes are key? Is tempo (time between events) important?
- Something non-science based?
- Perspective matters: Understanding the history of biodiversity and critical landmarks in life on Earth help us analyze current changes on Earth
The Earth is old…and it took a while for life to form.
- Surface was way too hot to start
- cooled enough to make a solid crust
- cooled enough sustain liquid water
- An atmosphere needed to form
- without an ozone layer, radiation from sun was too intense
- oxygen needed to accumulate for animals
- Lots of inorganic molecules but few organic molecules
- organic = carbon based compounds (basic building blocks of life)
Can life begin with just chemicals?
- Background: In the 1950s, scientists were curious about how life began on Earth
- Miller and Urey (University of Chicago) wanted to test if life’s building blocks could form naturally.
- The Experiment: They recreated early Earth conditions in a lab (water, gases like methane, ammonia, and hydrogen)
- Simulated lightning with electric sparks (energy source)
- Goal: To see if simple chemicals could turn into more complex molecules needed for life
Miller & Urey: A big discovery in a small flask
- Results: After a few days, they found amino acids—basic building blocks of proteins and life
- Why It Matters: Showed that organic molecules (like those in living things) can form naturally from simple chemicals
- the first step of creating life from non-living matter IS possible
- Legacy: transformed a philosophical question—‘Where did life come from?’—into a testable scientific one
- understanding how biology might come from chemistry is key for understanding life on other planets
Origin of heredity was key for contempoary life
- RNA World Hypothesis: Suggests RNA was the first hereditary molecule, capable of both storing information and catalyzing reactions
- Somewhere between the formation of RNA and cellular life a mechanism to pass genetic information from parent to offspring emerged (heredity)
- Heredity is the key for evolution of life and biodiversity
- replication → variation → competition → natural selection
- mutations (replication mistakes) are the unit of variation
- Heredity likely took place in primitive cells with compartmentalized RNA
- research on synthesizing ‘protocells’ and hereditary control mechanisms is ongoing
- we can’t yet fully replicate the spontaneous emergence of heredity yet.
Cellular life begins ~3.5 billion years ago (key events)
- LUCA: the Last Universal Common Ancestor — the most recent common ancestor of all current life on Earth.
- formed shortly after stable oceans form, likely near a deep sea vent
- ~3.5-3.8 bya
- first organism was a prokaryote - single-celled with no organelles
Single-celled organisms ruled and changed the world
Key events: evolution of photosynthesis, oxygen revolution, endosymbiosis->Eukaryotes
Early animal life and the Cambrain Explosion
Why did the Cambrian period explode? (still marine life)
All major phyla exist by Cambrian (530 million years ago)
Next rapid diversification occurred on land (400 MYA)
Starts with colonization by fungi and plant ancestors
Generated new habits/resources for land animals to evolve
Insects → amphibian/reptiles → mammals → humans
Animal life you are most familiar with are recent additions
This time period also aligns with the formation of the Appalachian mountains
The diversity of life on earth is shaped by evolution
The diversity of life on earth is shaped by creation and removal
Speciation events (and thus diversification) can happen quickly
Large extinction events disrupt the progress of diversity
